Titanium base alloys containing silicon



Patented Dec. 1, 1953 TITANIUM BASE ALLOYS CONTAINING SILICON Earl F. Swazy, Richard H. Freyer, andLee S. Busch, Indianapolis, Ind., assignors, by mesne assignments, to Mallory-Sharon Titanium Corporation lndianapolis, Ind., a corporation of Delaware No Drawing. Application January 13, 1950, Serial No. 138,516

.2 Claims.

This invention relates generally to alloys of titanium and has particular reference to alloys consisting of titanium, carbon and silicon, alone, or in combination with another element, to form a quaternary alloy with titanium predominating.

An object of the present invention, therefore, is to provide wrought, ductile alloys of titanium.

Another object of the present invention is to provide a wrought, ductile alloy of titanium, carbon and silicon.

Still another object of the invention is to provide quaternary alloys of titanium.

Yet another object of, the invention is to provide alloys of titanium consisting of titanium, carbon and silicon having greater resistance to oxidation at elevated temperatures than pure titanium a d exhibiting good hardness characteristics thereof.

Another object of the invention is to provide an alloy of titanium consisting of titanium, carbon and silicon and any one of the following elements:' aluminum, copper, vanadium, chromium, boron, tungsten and iron.

Still another object of the invention contemplates a method of preparing ternary alloys of titanium consisting of titanium, silicon, and carbon with titanium predominating.

Yet another object of the invention contemplates a method of preparing quaternary alloys of titanium consisting of the ternary alloys of carbon, silicon and titanium, to which is added an element from the group; aluminum, copper, chromium, vanadium, boron, tungsten or iron.-

Another object of the invention is to provide a method of fabricating ductile, hot forged alloys of carbon, titanium, and silicon, to which may be added any one of the elements: aluminum, copper, chromium, vanadian, boron, tungsten or iron, said alloys having a tensile strength exceeding 100,000 p. s. i. and more generally that above 120,000 p. s. i.

The invention, in another of its aspects, relates to the novel features and principles teaching the objects of the invention and to the novel principles employed herein whether or not these features and principles may be used in said object or in said field.

It is found that alloys of titanium, silicon and carbon with titanium predominating as a ternary alloy, 01' as an alloy to which may be added another element such as aluminum, chromium, copper, vanadium, boron, tungsten or iron provide a resistance to oxidation at elevated temperatures greater than that of .pure titanium. Such alloys provide ductile, strong alloys of titanium and exhibit good corrosion resistance and high hardness characteristics at elevated temperatures. These alloys are usually manufactured by melting and casting in a graphite retort under an inert or neutral atmosphere; for example, argon, or in a vacuum. Further, the alloys may also be prepared by powder metallurgy methods. Thus, as an example, alloys containing .1% to 10% silicon, .2% to 2% carbon with the balance titanium, as compared to pure titanium, are characterized by having a higher tensile strength, equivalent ductility, slightly higher electrical resistivity, much better resistance to oxidation at elevated temperatures and high hardness at temperatures up to 600 0, Further they may be hot or cold Worked by the usual methods known to the art.

As a further example hereof, an alloy made by mixing silicon powder and titanium powder or sponge, and melting and casting in graphite in argon gas, contained 0.992% silicon, .47 carbon, with the balance titanium. This alloy had the following properties as hot forged to reduction in area (equivalent properties of titanium containing (477% carbon only are included for comparison) Moreover, alloys, such as above, are characterized by a unique response to heat treatment. Upon quenching from 1000" 0., these alloys do not harden appreciably (most alloys of titanium which contain metals forming stable carbides do harden on quenching). However, as the tensile strength is lowered to 1 3,500 p. s. i., the elongation increases to 16.5%. In the as forged condition, the hardness at 600 C. increases from 0 Rockwell A to 32 Rockwell A when quenched. These changes are apparently caused by the presence of large amount of B titanium (body centered cubic) which is not transformed to a on fast cooling from 1000 C.

Again, in resistance to scaling tests at 900 C., an alloy containing .992% silicon was three times as efiective as that for titanium containing 47% carbon. The results revealed a 536% increase in weightfor the silicon alloy and 1.89% for the titanium alloy containing carbon only.

The ternary alloy consisting of titanium, silitemperatures e. g. 1000 C." The quaternary alloys of aluminum, silicon, carbon and titanium, may be manufactured in a manner similar tothoseof the ternary alloys; that is, they may be fabricated by melting and casting under an inert .or neutral atmosphere (for example, argon) or in a vacuum. The alloys may also be prepared by powder metallurgy methods. 'A preferred: method. con- 'sists of mixing aluminum and silicon, in mass or powder form, with titanium in sponge or powder form and then melting and casting in graphite. These alloys are preferably forged in air at temperatures between 800 C. to 900 C. but may be hot or cold worked by the usual methods known to the art.

These alloys may contain, small but significant amounts of aluminum, silicon and carbon; that is, upto 5% aluminum, ,up to 5% silicon; and up to 2% carbon. 'The .lower limit established is 0.1% aluminum, 0.1%,silic'on, 0.1% carbon. A practical range .of composition .is from, 0.5% to 3% aluminum; from 0.5% t3% silicon; from 0.3% to 0.7% carbon and'the balance titanium. Such an alloy (titanium; silicon, carbon,. aluminum) prepared by this invention has the following minimum properties:

Ultimate tensile strength"--. 120,000 p. s. i.

.Elongation in 2" percent. -Modu1us of elasticity x10 p. s. i.

Electrical resistivity '75 10-'ohm.-cm.

As stated, the ternary alloys formed of' titanium, silicon and carbon may be combined with one of .the. elements: aluminum, copper, chromium, :vanadium, boron or tungsten to form Thus, such an alloy consistquaternary alloys. ing of titanium, copper, silicon and carbon exhibits the characteristics recited previously for the above alloys; 1. e., ductility, high resistance "to oxidation, better corrosion resistance, higher hardness, etc.

. Thesealloys' (titanium, copper, silicon andoarbon): may be manufactured by melting and cast- .ing under. an inert or neutral 'atmosph'ere'(for example, argon) or ina vacuum. The alloys may also be prepared. by powder metallurgy methods. :A preferred method would thus consist in mixing copper and silicon, in massive or-powder-form, withtitanium in sponge or powder form and melting andrcasting in graphite. The-source of -thezcarbon is the crucible and :the amount is .easily controlled by varying the time th'at the "charge is molten. i The alloys-are preferably forged'in air at temperatures between 800C. and

900 C. but may be hot or :coldworkedby the usual methods. known to the art.

- The quaternary'alloys of titanium, copper, silicon. and carbon, herein'described, may be-made containing small but significant amounts of copper, siliconand carbon: for example, up to 10% copper; up to 10% silicon; and up to 2% carbon 4 with the balance being titanium. The lower limit for these alloys is 0.1% copper; 0.1% silicon; 0.1% carbon and the balance titanium. A practical range of composition may be 1% to 5% copper; 0.5% to 3% silicon; 0.3%'to 0.'7 carbon and thebalance titanium.

Such alloys prepared by this invention have the following minimum properties:

As hot quenched forged from 600 0.

,Ultin1atc tensile strength p. s. i 125, 000 150,000 Elongation in 2 pcrccnt 8 3 Modulus of elasticity p. s. i. 15Xl0 18X10 Electrical resistivity ohm-cm 7.5)(10- 75Xl0- I Still other alloys may be fabricated of titanium,

chromium, silicon, and carbon. These are also formed as by melting and casting under an inert .or neutralatmospheretfor example, argon): or in a vacuum. -Again. such alloysmayalso be .pre-

.paredas by powdermetallurgymethods.: For ex- ...ample, in the fabrication of this alloy,- a preferred method consistsof mixing chromium andsilicon in massive. or powder form, .with-. titanium in sponge .or powder form andmelting-and-casting .in graphite. The source of the carbomonce-more, vis'the crucible and the amount thereof .is easily controlled as by varying the time that the'charge is molten. The alloys of. titanium, carb on, chromium and silicon are preferably forged in air-'at temperatures between 800- C.-to 9009- C. but may be hotor cold worked by methods .known tozthe art.

.Such alloys contain -.small=.-.but significant amounts of chromium, silicon -and-;carbon;- that is, up to 10% chromium; up to 5% silicon and ,up to 2% carbonwiththe balance-being,- titanium. The lower limit is 0.1% chromium,-.0.'1.%': silicon, 0.1%carbon andthebalancetitanium. Apractical range of this composition isfrom 1% to 51% chromium; from .5-% to 2%.silicon; from 0.3% to 0.7 carbon and the balancev titanium.

' Alloys of. titanium, carbon, chromium, and. silicon by this invention havetheiollowing-minimum properties:

Ultimate tensilestrengthun. 125,000 p. s. i.

Elongation in 2" 5 percent. -.Modulus of elasticity -18 1'0 p. s. i. j Electrical resistivity 75 l0'- ohm-.=cm.

As an example 'ofthe formation of fabrication of, an alloy utilizing, the ternary .basealloy. tita- 'niu mpsilicon and 'carbonand an added element,

such as vanadium, is analloy consistingbf-snlall "but significant amounts of vanadium, siliconand carbon; thatis, up to 10 vanadium;,-.up .-to. 5% silicon; and upto 2%, carbon, with'the-balance being titanium." 'I'helower'limit for theall oy is "0.1% vanadium, 0.1% silicon and .0.l%- carbon and the balance titanium. .Apractical range of the composition-is 1% to 5% vanadium; 0.5% to 3% silicon; 0.3% to 0.7% carbon with the balance titanium.

-As with the "other alloyspthese alloysvexhibit better resistance to oxidation 'atielevated temperatures, better corrosion resistance,- higher .ultimate tensile strength and higher hardness at elevated temperatures than does pure titanium. In addition these alloys are characterized .as being adequately ductile and susceptible to hardening by quenching in water or other media.

'-The alloys 'of this invention may beimanufactured by melting and casting under .an inertor neutralatmosphere (for example, argon) or in a vacuum. The alloys may also be prepared by powder metallurgy methods. A preferred method consists of mixing vanadium and silicon in massive or powder form, with titanium in sponge or powder form, and melting and casting in graphite.

The source of the carbon is the crucible and so the amount is easily controlled by varying the time the charge is molten. The alloys are preferably forged in air at temperatures between 800 C.

to 900 C. but may be hot or cold worked by the methods known in the art.

These alloys prepared have the following minimum properties in the hot forged condition:

Another quaternary alloy which may be fabricated from the ternary alloys of titanium, carbon and silicon is the alloy of boron, silicon, titanium and carbon. Alloys thus formed are ductile and are stronger than pure titanium. They have considerably better resistance to oxidation at elevated temperatures and like the other quaternary alloys described exhibit-better corrosion resistance and higher hardness at elevated temperatures than those of pure titanium. For example, the resistance tooxidation at 900 C. is found to be much better than pure titanium or titanium with carbon present only. The alloys of titanium, silicon, boron and carbon may be fabricated as described by the methods above; such as melting and casting in an inert and neutral atmosphere (for example, argon), or in a vacuum. These alloys, too, may be prepared by powder metallurgy methods. Thus, a preferred method consists of mixing silicon and boron in massive or powder form with titanium in sponge or powder form and melting and casting in a graphite crucible. Since the source of v the carbon is the crucible, the amount is easily controlled by varying the time the charge is molten. The alloys may be forged in air at temperatures between 800 C. to 900 C. and may be hot or cold worked by the methods known to the art.

The alloys of titanium, carbon, silicon and boron as here described, may be made consisting of small but significant amounts of silicon, boron and carbon: that is, up to silicon; up to 5% boron; and up to 2% carbon; the balance being titanium. A practical range of composition is .5% to 3% silicon; 0.5% to 2.0% boron; 0.3% to 0.7% carbon; the balance being titanium.

These alloys have the following minimum properties in the hot forged condition:

Ultimate tensile strength 120,000 p. s. i. Elongation in 2" per cent. Modulus of elasticity 10 p.s. 1. Electrical resistivity 65 10 ohm-cm.

These alloys, utilizing tungsten, may be similarly manufactured as previously described and also may be prepared according to powder metallurgy methods.

For example, a preferred method consists of mixing tungsten and silicon in massive or powder till and melting and casting in graphite. Again, the source of the carbon is the crucible or retort so the amount is easily controlled by varying the time the charge is molten. The alloys are preferably forged in air at temperatures between 800 C. and 900 C. but may be hot or cold worked by the usual methods known to the art.

The alloys of titanium, carbon, silicon and tungsten, here described, may be made containing small but significant amounts of tungsten, silicon and carbon: that is, up to 10% tungsten; up to 5% silicon; and up to 2% carbon; the balance being titanium. The lower limit therefor is 0.1% tungsten; 0.1% silicon; 0.1% carbon; and the balance titanium. A practical range of composition is 0.5% to 5% tungsten; 0.5% to 3% silicon; 0.3% to 0.7% carbon; and the balance titanium.

Alloys thus prepared have the following minimum properties: i I

Again a base alloy of titanium, silicon and carbon may be combined with the element, iron, to form a new quaternary alloy titanium, iron, silicon and carbon. These alloys of titanium iron, silicon, and carbon are ductile and provide alloys of titanium which are stronger than titanium and have better resistance to oxidation at elevated temperatures. These alloys further exhibit better corrosion resistance and high hardness at elevated temperatures than those of pure titanium.

These alloys are characterized by adequate ductility even though the ductility is less than that of pure titanium; Moreover, the alloys of this invention are susceptible to hardening by quenching in water or other media. Alloys in the quenched state have ultimate tensile strengths of approximately 175,000 p. s. i. and elongation in 2" of about 4%.

The alloys of this invention containing iron may be manufactured by melting and casting under an inert or neutral atmosphere (for example, argon) or in a vacuum. The alloys may also be prepared by powder metallurgy methods. A preferred method consists of mixing iron and silicon in massive or powder form with titanium in sponge or powder form and melting and casting in graphite. Since the source of the carbon is the crucible the amount is easily controlled by varying the time the charge is molten. The alloys are preferably forged in air at temperatures between 800 C. to 900 C. but may be hot or cold worked by the usual methods known to the art.

The alloys herein described may be made containing small but significant amounts of iron. silicon and carbon; that is, up to 10% iron; up to 5% silicon; up to 2% carbon; and the balance titanium. The lower limit is 0.1% iron; 0.1% silicon; 0.1% carbon: and the balance titanium. A practical range of composition is 1% to 5% iron, 1% to 3% silicon, 0.3% to 0.7% carbon and the balance titanium.

Alloys of iron prepared according to this inven- Thefollowing chart is useful indepicting the constituents of the above described alloys.

ALLOY TABLE Alloy Ti Si O and Percent Percent Percent (2)"Ti, S1, C ALL. 99. 7-88 1- 5 l-2 l% Al (3) Ti, Si, O Cu 99. 7-78 .1- l-2 0 140% C11 (4) Ti, Si, O C1... 99. 7-83 .1- 5 l-2 0 ll0% Cr (5) Ti, Si, O V"... 99. 7-83 1- 5 l-2 0 ll0% V (6) Ti, Si, C B 99. 7-88 l- 5 l? 0 l-5% B. (7) Ti, Si, O W 9937-83 .l- 5 l-2 0 l10% W. (8) Ti, Si, O Fe-" 99.7-83 .1- 5 l-2 (Ll-10% Fe Thus, it is seen that by the present invention primary, ductile,'ternary alloys of titanium, sili-- con and carbon may be formed presenting characteristics substantially superior to pure titanium in matters of resistance to oxidation, resistance to corrosion and high hardness. In addition, these ternary alloys may be combined with any one of the elements;aluminumycopper, chromium, vanadium, boron-,tungsten or iron. Thus, a basic ternary alloy consists of from .1% to 10% silicon; from 12% to 2% carbon withthe remainder being substantially-all titanium. Several of the quaternary alloys may consist of up to 10% silicon; up to 2% carbon; and up to 10% of either chromium, vanadium, tungsten or iron; the remainder being substantially all titanium. Further, quaternary alloys of titanium,- silicon, carbon and aluminum; and titanium, silicon, carbon and boron may be fabricated wherein the silicon is present inamounts 'up to'5% carbon in 'amounts'upto 2%; and either aluminumor boron in amounts un to" 5% -offthe alloy;' the remainder ofi the total amount being supplied by the titanium. Again, an alloy; according to this invention 'may be fabricated- 0f titanium, silicon, car-bon and-:copper. In such an alloy, silicon, 1 and copper each may be present amounts up to 10%; carbon up-to- 2%;' withthe remainder thereof being titanium;

While the present invention as to its objects is merely illustrative and not-exhaustive in scope andsince many widely different embodiments of the invention may be made 'without departing from'the scope-thereof, it is intended that all matter contained in the above description be interpreted as illustrative and not in a limiting sense.

What is claimed is:

1. An-allo'y consisting of from'about- .1 to 10% silicon, fr'om-'.2% to 2% carbon; and the balance titanium.

2.An alloy consisting essentiallyof from".1% to 5% silicon, .2%* to 2% 'carb'on,flthe "balance titanium which onouenchin'g from900C.to 1000 C. has a hardness at 600 C. of 25 to 35 Rockwell A.

EARL F. SWAZY'; RICHARD H. FREYERL LEE S. BUSCH.

References Cited in'the file ofthis" patent UNITED STATESPATENTS Number Name Date 2,267,298 Dean Dec'..23,'1941 2,270,660 Misfeldt .Jan." 20,; 1942 2,287,888 Kroll June.30, 1942 2,490,570 Anicetti Decpfi, 1949 OTHER REFERENCES Zeitschrift. fiir Metallkunde, vol..-29,. page 190 "Titanium, Report of Symposium, December 16,1948, sponsored by the. Oflijce of NavalResearch, Dept. of the. Navy, pages 73-76;

Product Engineering, November 1949, page 148. 

1. AN ALLOY CONSISTING OF FROM ABOUT 0.1 TO 10% SILICON, FROM .2% TO 2% CARBON, AND THE BALANCE TITANIUM. 